The present disclosure relates to line frequency detectors and, in particular, to detecting the line frequency of a power source for a dimmable solid-state lighting device.
Solid-state lighting devices can be connected to a wall dimmer to provide a user with a way of varying the brightness of the lighting device. A wall dimmer typically receives electric power as a sinusoidal waveform (e.g., an AC power source at a line frequency of 50 Hz or 60 Hz) and performs phase cutting on the waveform to generate an input voltage for the lighting device. A controller in the solid-state lighting device measures the phase angle of the phase cut and causes a driver circuit to generate an output current at a corresponding power level for a solid-state light source (e.g., a light-emitting diode) in the lighting device.
One drawback to these types of dimmable solid-state lighting devices is that they are sensitive to changes in the line frequency. A change in line frequency can lead to a significant malfunction in the lighting device if the controller is unable to detect a change in frequency and make corresponding adjustments when generating the output current.